The aim of this paper was to examine if, as assumed in the tonal hierarchy construct, listeners understand octave-related tones as having the same tonal stability regardless the melodic patterns where tones are inserted. Three studies were conducted, in which both musicians and non-musicians were tested. In Study 1, participants judged how well a set of melodic fragments were 'continued' by several probe-tones. In Study 2, participants judged how well fragments were ‘completed’ by the same probe-tones. And in Study 3 participants judged how well fragments were ‘completed’ by probe-fragments. An unanticipated result was that the task affected musicians’ judgments, but not (or at least not clearly) non-musicians’ judgments. Regarding the initial aim of the paper, it was observed that musicians tended to judge octave-related probe-tones as having the same tonal stability. Non-musicians, however, did not; their judgments showed an effect of tonality only when probe tones that had occurred in the given fragments or that were close to them were considered.